The impact of elevated atmospheric carbon dioxide (CO₂) on physiochemical parameters in food crops remains incompletely understood. In this study, we cultivated three peanut genotypes under ambient (400 ppm) and elevated (650 ppm) CO₂ conditions. The total phenolic content (TPC) and antioxidant capacity of the vegetative matter and seeds were investigated using the Folin-Ciocalteu method, FRAP and CUPRAC assays. Additionally, the crude protein content (CP) was determined by measuring nitrogen content through combustion. High values of TPC were observed in the shoots and roots of all genotypes, with non-significant variations noted between the treatments. However, the seeds showed lower levels of TPC, with a negative trend in all three genotypes in response to elevated CO₂, although this difference was not statistically significant. Moreover, there were no significant difference between the ambient and elevated CO₂ treatments. The CP content varied significantly among the genotypes. In addition, the CO₂ treatment did have a significant impact on protein concentration within each genotype. Under elevated CO₂ conditions, Holt demonstrated a moderate increase (4%) and Alloway showed a slight increase (6%) in protein concentration, whereas Kairi experienced a small decrease (-1%). It is noteworthy that despite the significant difference between the CO₂ treatments, Kairi exhibited the highest overall CP percentage (29%). These findings imply that future atmospheric scenarios featuring increased atmospheric CO₂ concentrations could potentially change the nutritional quality of our food. Therefore, this study provides valuable insights into the potential impacts of elevated CO₂ on the nutritional quality, enabling better preparedness for the future.